walmartlabs / object-diff

A Go library implementing object wise diff and patch.

Object-Diff

This library is designed to provide a mechanism to compare two objects and compute a difference. That difference can then be applied to other objects, performing a selective update to an object.

This library was designed to solve a common problem in Kubernetes operator development, but has been designed to be as general purpose as possible. Bugs and pull requests are welcomed and encouraged.

Shortcomings

This library is primarily designed to move an object from one state to the next as in A -> B -> C, if trying to enact something like A -> C there is no guarantee that all changes can be captured and could result in partial, possibly incomplete, objects. This should generally be in line with what is expected of a diff and patch algorithm, but can have unexpected consequences.

Improvements and Future Work

• Currently the tests are lacking and there are possibly cases which are not covered or behave badly. Work on this area is currently in progress.
• Comparision of arrays and slices is currently only by index, future work is planned to provide plugins/callbacks which allow to provide an identity for a particular object in an array or slice and compute the difference based on that.
• For instances when you want to ignore certain known changes, providing a mechanism for exclusions is future work.
• Renaming a map key results in a delete and addition.
• Example usage as part of a Kubernetes operator is currently a near term goal.